Optical device



J. R. KERRY OPTICAL-DEVICE Filed July 23, 1942 I v 4 Sheets-Sheet 1 Nov. 20, 1945. J. R. KERRY OPTICAL DEVICE Filed July 25, 3.942

4 Sheets-Sheet 2 Nov.- 20, 1945.

J. R. KERRY OPTICAL DEVICE Filed July 23. 1942 4 Sheets-Sheet 4 Patented Nov. 20, I945 orr cs OPTICAL DEVICE John R. Kerry, Palatine,

assignments, to Amer! Southbridge, Masa, a voluntary association of v Massachusetts can Optical Company,

- Application my 23. 1942, 801181 No. 451,997

scuums.

This invention relates to an optical device, and more particularly to a device for accompl the complete separation of the visual fields of a pair of eyes and adapted for use in the examination measurement and training of eyes in their several functional performances.

An object of the invention is to provide a device ior measuring the comparative magnification of images between two eyes of a patient. Another object is to provide apparatus for determining and measuring phorias or muscular imbalance of each of the eyes of a patient. Still another object is to provide apparatus for independently testing and measuring vision of each oi a pair of eyes. I

Another object of the invention is to provide in an optical device separate fields of vision for each of a pair of eyes and to separately measure the vision or the eyes. Yet another object is to provide a pair of visual targets in adjacent relation on a target surface and mechanism for maintaining each target in the field of vision of only one of a pair of eyes.

A further object is to provide a pair of visual targets in adjacent relation on the same target surface and means for providing a path of vision between one of a pair of eyes and one target and between the other eye and the other target together with means vision at periodic intervals, the intervals being so short as to provide substantial continuity of vision for each eye with respect to the target which it observes.

Another object of the invention is to provide a pair of visual targets in adjacent relation on a target surface and mechanism for adjusting the position of one of the targets with respect to the other to bring the targets relation with respect to the Yet another object is to provide a mechanism for adjusting the position of the targets on the surface with respect to each other and for measuring the adjustment. Still another object isto prowhich- Figure l is a perspective view of a device embodying the invention;

for interrupting each path of' of the targets:

26 the same surface showing the 1 position; Fig. 15 is a fragmentary detail perspecother embodiment of the into a predetermined vision of the observer.

' to cause vide an adjusting mechanism for simply and easiiy changing the position of one of a pair of tar- '45 longitudinal sectional view taken along the line 2-2 of Fig. 1; Fig. 3 iso transverse sectional view taken along the line H of Fig. 2; Fig. 4 a transverse sectional view taken along the line of Fig. 1; Fig. 5 is a transverse sectional view taken along the line 5-5 of Fig. 1; Fig. 6 is a fragmentary horizontal sectional view taken along the line 8-6 of Fig. 1 and showing, in elevation; the crank arm actuating means for operating the mechanism for adjusting theposition Fig. 7 is a detail fragmentary sectional view taken along the line of Fig. 2; Fig. 8 is a fragmentary perspective view of the mechanismfor adjusting the lines of the target; Fig. 9 is a front eievational view of a target surfaceshowing a pair of visual targets thereon; Fig. 10 is a similar view with the targets adjusted in position to bring them into cooperative relation; Fig. 11 is a front elevational view of a target surface showing another pair of targets; Fig. 12 is a similar view of the same surface with the targets in adjusted position; Fig. 13 is a front elevational view or a target surface showing another pair of targets; Fig. 14 is a similar view of targets in adjusted tive view of an adjusting cam and the frame member carried thereby; Fig. 16 is a diagrammatic view showing the optical arrangement of the embodiment of the invention sh'own in Figs. 1 to 15; Fig. 17 is a diagrammatic view of aninvention; and Fig. 18 is a diagrammatic view of another embodiment of the invention.

It has heretofore been found that the eyes of a person may possess different power to magnify objects which are observed and retinal images of diii'erent sizes may be produced by the two eyes. This eflect may be present whether or not the person wears glasses. A difference in the magnii'ying power of the two eyes has been found fatigue to the patient as a result of the of synchronizing the retinal images of sizes. The present invention contemplates a device by means of which the diflerence in magnifying power of the two eyes of the patient may be determined and measured so that lenses may be provided to compensate for this difference. .The device is also suitable for determining and measuring phorias or muscular imbalances of the eyes of a patient and for testing in other respects the vision of the patient.

In the embodiment of the invention described dimculty difl'erent 3 i8 8 ntary herein and referring particularly to Fig- 1, the

deviceincludesabaseilisu ortingapairofveraperturesillustr'etedinrlsa3and4beingpartical frame members ii and i2 which, in turn. ticularly suitable forthedetermin tion and messsupport between them a horizontal platform II. urement of difference in the powers of magnificacarrles a horizontal member i4 which acts as a shield for the eyes of the patient and is equipped with a pair of apertures II and I which may be placed before the eyes of the patient. At the opposite ends of the member l4 are the housings l1 and II which may be supported in position in any suitable manner and which are arranged to receive lamps II and 20 for projecting avisualtarget.

Horizontal supports 2| and 22 are pivotally supported by the frame member If and extend outwardly therefrom. .On the supports 2i and 22 are moimted the tubular casings 23 and 24 which provide an optical system for the projection of an image. The frame member 25 supports one end of a shaft 24 on which are mounted cams 21 and 24 beneath the supports 2i and ,22 respectively. The c te end of the shaft 24 is supported by another frame member (not shown) carried by the member i2.

As seen particularly in Fig. 2, the prc:lection system includes the housing l8 and the lamp 2. moimted therein. The lamp 20 may be carried by any suitable socket 28 having a connection 20 leading to a suitable source of electric current. A pair of lenses 3i and 32 serve to concentrate and focus the beam of light on one side of the lamp. The beam of light from the lamp passes through the lenses 2i and 32 and into the casing 24 which is equipped with a plate target. A lens 34 at the end of the tubular casing 24 focuses the beam of light which is proiected therefrom.

A tubular shutter 35 is interposed between the housings i1 and I8 and behind thecasings 23 and 24 respectively. The shutter may be of any'suitable construction and is preferably a tubular member equipped with apertures 24, 31; 38 and 3!, the apertures 38 and 31 being in longitudinal alignment with each other and the apertures 38 and 8! being in longitudinal alignment with each other and being disposed at an angle of 90 with respect to the apertures 28 and 31 on the periph cry of the tubular shutter 25. The shutter 25 is provided in each case with an aperture directly opposite the enumerated apertures so as to per- The platform ll mit a beam of light to pass throu h the shutter.

Thus, the shutter is equipped with the aperture 34'- opposite the aperture 38 which perm s he beam of li t t pass from the housing ll into the casing24. 'I'he shutter 35 s rotata ly sunported by the frame members ii and i2 and is arranged to be driven b a belt 40 carried bv he pulley 4| on the motor 42. Preferably. th motor is equi p d with a rubber mountin to d crease the vibration caused by the operation of the sa e and may be supported by an extension 48 of the platform is.

As seen part cularly in Fi s. 3 and 4. the e ings 22 and 24 are eouinned intermedia e their ends with lu s 44 and 4! for manor-ting the nlat s I 44 and 41 respectively. The central nortinm of a are anertured as at II and 42 in order to permit the beams of li ht i casin s to pass throu h thenlates. Wi s BI and m unted at 2 and B3 on the pla e 41 extend the plates 44 and 41 a partia l acro s the aperture 4! while s milar wires I4 and I5 extend part all nm'n gt e ape ture 48. These wires pr vide smcerl lines (m the visual tar ets which are form d on t e tar t surface by the two projectors. The apertures 48 and 4! may be of' any suitable size and shape, the

and is received tipn of the two eyes of the patient.

Thecasing 24 may oonsistof apairoftubular members I. and I! received telescopically within each other in fixed relation. If desired, the members may be arranged for longitudinal telescopic adjustment to permit adjustment of the focus of the beam of light passing through the casing 24. The member 51 may be equipped with a transverse slot 48 intermediate its ends. In alignment with this slot II the tubular member 58 is equipped with an internally threaded opening 5! for threadedly receiving the bolt 44. The bolt 40 extends downwardly from the tubular casing 24 and is equipped with shoulder II for engaging the support 2i and is provided with a thumb'screw head 42 for tightening thecasing 24 against the sup ort 22. The bolt it asses through anaperture in the end of the rod 48 thereby.

As seen particularly in Figs. 1 and 6, a tumbuckle 84 of the conventional type connects the 41 for forming a visual ranged so mounted on the crank 44. 61 is attached to'the oppo- 46 and connects through a a similar mechanism for engaging the casing 28. A shaft 49 secured to the center of the crank disc 44 and extending downwardly therefrom is equipped with an inwardly turned lower portion .10 and a. handle 1i for turning the shaft.

Rotation of the shaft 69 produces rotation of rod to an arm A similar crank arm site side of the disc turnbuckle 88 with the disc 64 and movement of the crank arms 4! and 61 to laterally shift the casings 23 and 24 toward or away from each other. The turnbuckles 84 and 48 may be used to adjust-the length of the crank arms which are connected to the casings 23 and 24.

Referring particularly to Figs. land 15, the cams 21 and 28 may be used to shift the vertical position of the casings 22 and 24. On the central portion of the shaft 20 is mounted a member 12 which receives the shaft 89.

cured to the-upper portion of the shaft 4! to;

flx the same in position with respect to the member 12. Movement of shaft is in a vertical plane thus produces rotation of the member 12 and rotation of the shaft 26. The earns 21 and 24 are rotated by movement of the shaft 24' and produce 9. raising or lowering of the casings 22 and 24. The cams 21 and 28 are preferably arthat the enlarged portions thereof are disposed at angles of 180 with respect to each other. In this manner, when the shaft is rotated to raise the casing 22, the casing 24 is lowered, while movement of'the shaft to raise thec'aslng 24 produces a lowering of the easin! 22.

As seen particularly in Fig. 15, the support 2i above the cam 21 may be equipped with an adjustable bracket 14 which engages the cam 21. A thumb screw I32 permits vertical adjustment of the bracket 14 wtth respect to the channelled support member 2!. In this manner, the vertical position of either the casing 23 or the casing 4 24 may be adjusted independently without move- The supports 2i and 22 for ment-of the other casing.

The frame members 25 are equ pped at their ends with charts 11 and 14 for measuring the vertical and horizontal displacement of the cas- 24 are equipped with depending pointers I8 and 15 which are disposed in adjacent relation to the charts H and I8. The pointers are constructed to provide an indicator for the vertical as well as the horizontal displacement of the casing. The ends of the casings may also be provided with pointers I9 and 88 which cooperate with the received within the journal 84 to rotatably support the end of the shutter.

Referring particularly to Figs. 4 and 8, the wires 54 and 55 may be supported by a pair of spaced members Bl and 88 which are turned inpreferably provided with a wardly toward eachother at their end portions 89 and 98. The members 81 and 88 are fixedly mounted in a support 9I within the housing 92. A depending lug 93 carried by thehousing 92 fixedly receives the micrometer body (on which the suitable scale 1, 2, 3, etc., is engraved) and supports it in a predetermined position. The micrometer screw plunger 94 undergoes longitudinal displacement whenever the micrometer headpiece 98 is rotated. A cam 95, having the shape of a frustum of a cone, is accurately fitted to the end ofshaft 94 and so .moves both rotationally and longitudinally with it. Spring tension within members 91 and '88 causes their inclined end portions 89 and 98 to rest in contact with opposite faces of cam 95 at all times. For this reason, any longitudinal change in the position of cam 95 causes a proportional change in the spacing of the members 81 and 88. The head of the micrometer 96 undergoes the same rotational and longitudinal displacement that shaft 94 undergoes and so is fitted with a driving pin, which in turn is .engaged slidably by a channel within the sleeve 91. Sleeve 91 is supported by and rotates upon an axle or spindle that projects rigidly (fixedly) from supporting.

member 9!. Sleeve 91 is so fixed that it is capable of rotational motion only. The worm gear 98 is rigidly fixed to sleeve 91. The worm gear 98 meshes with the worm 99 on the shaft I88 which, in turn, is connected to the flexible shafting I8I. The flexible shafting I8I, leads to a crank I82 (Fig. 1) by means of which the shaft I88 may be rotated to shift the longitudinal position of the shaft 94.

The micrometer 98 may be of conventional construction and need not be described in detail herein. It is sufllcient that the micrometer be adapt ed to measure precisely small longitudinal changes in the position of the shaft 94 and the cam 95 carried thereby. When the crank I82 is'operated, the worm 99' and gear 98 are rotated. The shaft, 94 and cam 95 carried thereby are longitudinally shifted and the movement of the cam produces movement of the. wires 54 and 55 toward and away from each other. With this mechanism extremely small changes in the distance between the wires 54 and 55 may be accurately obtained and measured.

The visual targets which are projected by the instrument may be of any suitable type. When the target-forming plates shown in Figs. 3 and' 4 are used, the target which is projected ,will beof the type shown in Figs. 9 and 10. This target may be projected upon a screen of the conventional type.

As seen in Fig. 9, the screen I89 may receive the visual targets I84 and I85 having therein the spaced parallel lines I86 and I 81 which are formed by the spaced parallel wires in the target-forming plates, When projected on the screen I83, the targets may have the appearance indicated in Fig. 9. The observer or patient, when using the instrument, adjusts the controls of the instrument until the targets are brought into the position in which they appear in juxtaposed relation as seen in Fig. 18, with the lines I86 in alignment with the lines I81.

The visual targets I84 and I85 are of similar contour patterns as shown in Fig. 9, which contour patterns, because of their similarity, possess fusible characteristics. It is due to these fusible characteristics that the said contour patterns will appear in juxtaposed relation with each other, as seen in Fig. '10, and will be retained in said relation only through said fusible characteristics. This is commonly known in the art.

For measuring muscular imbalances, the type of target shown in Figs. 11 and 12 has been found to beparticularly suitable, As seen in Fig. 11,

the screen I88 receives the targets I89 and II 8,

the targets being provided with angular lines III and I I2. With this type of target, the patient and observer adjusts the position of the targets until the lines III and H2 are in the relation seen in Fig. 12.

Another type of, target which may be used is that seen in Figs. 13 and 14 where the screen H8 receives a pair of targets H4 and H5 bearing legends H6 and II I, of any desired type. The patient or observer may bring the targets into such relation as to provide a continuity between the legends H8 and II! appearing on the two separate targets.

It is to be noted that the targets II 4 and H5 are of similar contour shape and are, therefore, fusible. It is through their fusible characteristics that the observer may bring the targets into such relation 'as to provide continuity between the legends H9 and II]. If the contour patterns of the targets I I4 and I I5, as commonly known in the art, did not possess fusible characteristics of the various targets by means of Figs. 10, 12-

and 14.

As seen particularly in Fig. 16, the device is equipped with a target surface I 83 upon which visual targets may be projected. -The lamp I9 provides a beam of light which passes through the lenses 8| and 92, through the apertures 98 and 96 in the shutter 45 and through the target-forming plates 48 and 41 and lens 34 to form a target on the, target surface I83, Similarly, the lamp 28 provides a beam of light which passes through the projection system of the casing 24. The eyes I84 and I85 of the patient or observer perceive the target through the apertures 31 and 98 in theshutter 35, the arrangement of the apertures in the shutter being such that the eye I84-perceivesthe target formed by the plate 41 and the eye I85 perceives the target formed by the plate the visual held of the eyes 4!. At the time that the tar et formed by the plate 4! is visible on the target surface I, the shutter 35 serves to intercept the vision of the eye I while permitting the eye III to perceive the target through the aperture 3|. Similarly, when the target formed by the plate 41 is visible on the target surface I03, the shutter 35 intercepts the vision of the eyelli while permittin the eye III to perceive the target through the aperture 31 in the shutter.

Other suitable arrangements of the target surface and shutter mechanism may be readily worked out. As seen particularly in Fig. 17,- the shutter may comprise a pair of tubes II! and I is. These tubes are provided with apertures I20, I2I, I22 and I23. The visual targets are projected on the target surface I24; The lamps I9 and 20 are disposed adjacent the apertures I20 and I2I respectively in the tubular shutter H8. The eyes Ill and I05 of the patient or observer are arranged adjacent the apertures I23 and I22 respectively in the tubular shutter H8. The tubular shutters H8 and 9 are rotated in synchronism so that the aperture I22 opens the field of vision of the eye IIII when the target formed by the light from the lamp 20 is visible on the screen or the target surface I24. At-the same time, the apertures I20 and I23 are closed. The. apertures I20 and I2: in turn are opened while the apertures I2l and I22 are closed.

As seen particularly in Fig. 18, the target surface may, if desired, consist of a translucent screen I25 disposed between theprojection system and the eyes of the observer. With this construction, a tubula shutter I2 equipped with apertures I21 and I2! is arranged adjacent the eyes I and Ill-5 of the observer. On the other side ofthe translucent screen I25 are the lamps I! and 20 and the projection systems forming targets from the beams projected by the lamps. A tubular shutter I2! equipped with apertures Ill light from the lamp IS. The tubular shutters I28 and I2! are rotated in synchronism so that when the aperture III is open and a target istormed on the screen I25 from the beam of light from'the lamp 2|, the aperture I2. will be open and the eye, III will perceive this target. Atihis time, the apertures I21 and I" areclosed. Simprovide continuity o! the retinal image which is' received by the observer.

terruption oi the projection of the visual targets. When one target is visible only one-eye may perceive it. When the other target becomes visible only the other eye may perceive it.

The visual targets which are formed on the screen or target surface may be of the character seeninFigs.9and 10 whereinapairoispaced parallel lines appear in the central aperture oi each 01 the targets. The patient, by adjusting the control lever II tomove the casings 23 and 24 in the vertical and horizontal planes, may

visual targets into adjacent rela- Ilit and III of the targets in approximate alignment with each other. This adjustment of the horizontal and vertical positions of the projection casings 23 and 24 permits the compensation for the muscular imbalances of the eyes 01 the patient.

When the lines Ill and III of the targets I04 and I" are in approximate alignment, the patient may then adjust the distance between the pair of lines III by operating thehand crank I". The operation of tliecrankeausesthecamtobeshiited longitudinally. This, in turn. causes equal and opposite shifts in the lateral positions oi! the members 81. and 88 since their spring tensions cause their respective inclined end portions 8! and II to'iollow the cam at all times. This causes a changein the spacing between wires H and II, Fig.4,becausethesewiresarerigidlyiixedto the extreme ends of members I! and II respe tively, and are free to move with these members.

The distance between the changes simultaneously and proportionately because these lines are the projectedimages ot wires ll and II. In'addition. the'spacingsbebring the two tion with the lines and m maybearranged adjacent the lamps II tween the li lla pmpqrfl wt m and 2|. The aperture in permits the passage or ings or the micrometer, and the n n of t s the beam of light from the lamp 2| while the m my be plotted srap i i Is M0118 aperture wi er-mite the passage ort m u of the micrometer scale readings. The adjustment of thecrank maybe continuedimtil the lines Illappeartothepatienttobespacedapart byexactlythesune distancebywhichthelines ted. The micromexist for the-two eyes ole niflcations that may ratio oi! the distance ilarly, when the aperture Ill is open d, permitpatient is measured by the tingtheiormationonthes'creenflioiavisual munfill'lmthemwmemm target mm the beam or light from the lamp ll. Br computing these ratios for several repthe aperture I21 is open and the eye"! perceives this target. At this time, the apertures I23 and III willbe closed.

The shutter is rotated at a speed which provides for the interception of the beam! 0! light of the projection systems and for the interception oi oi the observer at a rate which permits continuity of the vision of the observer. By this is meant that the fields 0! vision 0! the observer and" the projection of the visualtargetsarein -tedatperiodicspeced intervals, the intervals beingniillclently short distance between lines the correw dins chart for the magnitude eyes of a p tient is before the instrument with theapertures II and the calibration chart the cation val Ieinthe frame llbeingbeiore the eyes'lll'and. eorrespondingtothemicrometerreadingrecord- III of the patient. The lamps I! and 20 of the ed for thatpatient.

projection system are lighted and the shutter with this instrument, any diiliculty in c set in rotation by operation or the motor 42. for phorias or muscular imbalances of lincall'linthetl-l'l t oithedifierenceinth emagwith a viewing screen, said use the type of target shown in Figs. 11 and 12 wherein a pair of angular lines are disposed within the central apertures of the target. With this type of target, the patient-is free to move element iii in any direction with respect to element H2. He does so until the vertices of the two angular elements appear to him to meet at the center of a symmetrical cross, as in Fig. 12. If there is no muscular imbalance, the targets on the screen will be exactly as shown in Fig. 12. If there is a muscular imbalance, they will be displaced relative to each other in proportion to its direction and extent. Fig. 11 shows a typical arrangement in which there is a combination of both a vertical and a lateral muscular imbalance. The magnitude of these imbalances is expressed in terms oi'the angular displacements, measured at the patients eye, in both the vertical and horizontal meridians.

The device may also be used for any of the usual type of visual acuity tests, and is particularly advantageous in that it provides a means of testing the vision of one of the eyes of the patient without actually shutting off the vision of the other eye and perhaps interfering with the tests on the first eye.

The targets of the type shown in Figs. 13 and 14 may be used for the usual vision tests and are particularly suitable in determination of malingering. These targets may be formed by inserting slides in the projection casings 23 and 24, or in any other suitable manner. The patient may be directed to place the legends which appear on the diii'erent targets in proper relation. If this is done, there is no question as to the vision of the patient in each of the eyes. Different types of targets may be used for each of the eyes and the legends may be of diilerent sizes, if desired.

Although the invention has been described in connection with specific embodiments and speciflc methods of operation, it is apparent that many changes and modifications may be made in the construction and operation of the instrument without departing from the spirit and scope of the invention.

I claim:

1. A device of the character described for use with a viewing screen, said device comprising means for producing test patterns for the respective eyes of an individual on said viewing screen, said test pattern means embodying means for producing area portions having fusible characteristics and embodying means for producing portions having dimensionally relatable characteristics within the fields of said area portions with the dimension of one of said relatable portions being variable relative to the dimension of the other of said portions, means for alternately rendering the test patterns separately visible to the respective eyes in successive sequence and at such speed as to provide continuity of vision, unitary means for altering the positional relation of said area portions and portions having dimensionally relatable characteristics both vertically and horizontally with respect to each other for positioning said area portions in fusible overlapping relation with each other and for simultaneously positioning the portions having dimensionally relatable characteristics in adjacent relation with each other and means for altering the dimension of one of said dimensionally relatable portions relative to the other.

2. A device of the character described for use device comprising means for producing test patterns for the respective eyes of an individual on said viewing screen, said test pattern means embodying means for producing area portions having fusible characteristics and embodying means for producing portions having dimensionally relatable characteristics within the fields of said area portions with the dimension of one of said relatable portions being variable relative to the dimension of the other of said portions, means for alternately rendering the test patterns separately visible to the respective eyes in successive sequence and at such speed as to provide continuity of vision, unitary means for altering the positional relation of said area portions and portions having dimensionally relatable characteristics both vertically and horizontally with respect to each other for" positioning said area portions in fusible overlapping relation with each other and for simultaneously positioning the portions having dimensionally relatable characteristics in adjacent relation with each other, means for altering the dimension of one of said dimensionally relatable portions relative to the other and means for altering the meridional relation of one of said area portions relative to the other.

3. A device of the character described for use with a viewing screen, said device comprising means for producing and for successively projecting test patterns for the respective eyes of an individual alternately on said viewing screen at periodic intervals, means for alternately rendering the test patterns separately visible to said respective eyes at such speed as to provide continuity of vision, said test pattern means 'embodying portions adjustable to appear in juxtaposed relation with each other on said viewing screen and embodying portions relatable as to dimensional characteristics. with the dimension of one of said relatable portions being variable relative to the dimension of theother relatable portion while retaining said juxtaposed portions in saidrelation.

4. A device of the character described for use with a viewing screen, said device comprising means for producing and for projecting a test I pattern for-each of the respective eyes of an ining portions dividual to be viewed on said viewing screen, means for providing separate paths of vision for each of the respective eyes for viewing said test patterns and unitary means having portions functioning cooperatively with the means for producing and projecting the test patterns and with the separate paths of vision for alternately and successively rendering the test patterns separately visible to said respective eyes with the speed of alternating being such as to provide continuity of vision, said test pattern means embodyadjustable to appear in juxtaposed relation with viewed on said viewing screen, means having a pair of sight openings therein for locating the head of an individual to be tested at a given position relative to said device and means having portions associated "with said respective sight openings and projectors for alternately and suceach other and embodying portionsrelatable as to dimensional characteristics, with 6 cessively rendering the test patterns separately visible to said respective eyes with the speed 01 able portions being variable relative to the dimension oi the other relatable portion while retaining said juxtaposed portions in said relation;

6. A device of the character described for use in combination with a viewing screen, said device comprising a pair of projectors embodying means for producing and projecting test patterns for the respective eyes of an individual to be viewed on said viewing screemmeans having a pair of sight openings therein for locating the head oi an individual to be tested at a given position relative to said device and means having portions associated openings and projectors for alternately and successively rendering the test patterns separately visible to said respective eyes with the speed of alternating being so controlled as to provide continuity oi vision, said test pattern means embodying portions adapted to be positioned in juxtaposed relation with each other and embodying portions relatable as to dimensional characteristies with the dimension of one of said relatable portions being variable relative to the dimension of the other relatable'portion, means for moving said portions capable of being positioned in juxtaposed relation with each other to said relation and means for varyins the dimension of one of the relatable portions to match the dimensional characteristics of the other of said relatable portions.

dimensional characteristics,

with said respective sight means "I. A device oi the character described for use with a viewing screen, said device comprising means for producing and for successively projecting test patterns for the respective eyes 01 an individual alternately on said viewing screen at periodic intervals, means for alternately rendering the test' patterns separately visible to said respective eyes at such speed as to provide continuity of vision, said test patterns means embodying portions adjustable to appear in juxtaposed relation with each screen and embodying portions relatable as to with the dimension of one of said relatable portions being variable relative to the dimension of the other relatable portions while retaining said juxtaposed portions in said relation and means for extent of said variation.

8.- A device of the character described for use with a viewing screen, said device comprising means for producing and for successively projecting test patterns for the respective eyes 01 an individual alternately on said viewing screen at periodic intervals, means for alternately rendering the test patterns separately visible to said respective eyes at such speed as to provide continuity of vision, said test pattern means embodying portions adjustable to appear in juxtaposed relation with each other on said viewing screen.

and embodying portions relatable as to dimensional characteristics, withvthe dimension of one of said relatable portions being variable relative to the dimension of the other relatable portion while retaining said juxtaposed portions in said relation and means for shitting the meridional relation of said relatable portions relative to each other.

JOHN R. KERRY.

other on said viewing determining the 

